This invention relates to a facility to draw off or store viscous mass which is discharged from a process for example as a result of exothermal events.
The invention has further reference to the use of the device in accordance with the invention to draw off or store solutions of cellulose in an aqueous amine oxide discharged from a process to produce cellulosic moulded bodies for example as a result of exothermal events and a process to draw off and store solutions of this kind.
It is known that when transporting viscous mass in chemical or physical processes safety precautions are taken whereby in the event of operational malfunctions the masses are in part discharged from the means of transport.
This covers in particular processes for the production of cellulosic moulded bodies from solutions of cellulose in an aqueous tertiary amine oxide particularly N-methyl-morpholine-N-oxide (NMMO). These processes are known as the "Lyocell process" or the "amine oxide process".
One problem when producing cellulosic moulded bodies by dissolving the cellulose in a mixture of NMMO and water consists in the stabilisation of mouldable solutions obtained in this way. It appeared that when dissolving the cellulose in NMMO the cellulose begins to decompose which leads to an undesirable reduction in the degree of polymerisation of the cellulose and the formation of low molecular decomposition products when the solution is subjected to a thermal load for longer periods of time at temperatures above 100.degree. C.
Moreover, amine oxides, and NMMO in particular, have a limited thermo-resistance which varies depending on the structure. The monohydrate of NMMO melts at temperatures of approximately 72.degree. C., the anhydrous compound melts at 171.degree. C. If the monohydrate is heated strong discolouring occurs at temperatures as of 120/130.degree. C. Temperatures of this kind are quite common with processes to manufacture cellulosic moulded bodies. As of 175.degree. C. strong exothermal reactions occur which can lead to an explosive procedure. In the course of these reactions NMMO is thermally decomposed mainly to N-methyl-morpholine, morpholine, formaldehyde and CO.sub.2.
Since the compounds which form at the prevailing temperatures tend in general to be gaseous high pressures arise with the exothermal decomposition of NMMO which can lead to damage to apparatus parts.
To be able to draw viscous mass off from the process in the event of operational malfunctions, safety apparatuses are know from the state of the art, as are for example described in DE 18 00 061, PCT-WO 94/08162 or PCT-WO 97/08482.
The expert is now faced with the task how this discharged viscous mass can be further drawn off or stored. This is particularly true of mass which congeals when it cools down and which can, therefore, no longer be pumped or only be pumped with difficulty, such as for example solutions of cellulose in tertiary aqueous amine oxides.
EP-A 0 626 198 suggests a cylindrical shaped receptacle which has an entry opening for a congealing material drawn off from the process and at least two entrance openings. By opening the two entrance openings the material can be pushed from one of the two entrance openings to the other and removed from the receptacle in this way.
This apparatus has the disadvantage that the drawing off of a congealed viscous mass from a receptacle like this in the way described is very complicated since the mass settles down on the receptacle wall when congealing and has, therefore, to be scratched off. Moreover, the known apparatus has the disadvantage that the mass drawn off from this process has to be transported across long distances through pipes to the receptacle. The mass can thereby already congeal in the pipes thus leading to blockages.